Oil sand generally comprises water-wet sand grains held together by a matrix of viscous heavy oil or bitumen. Bitumen is a complex and viscous mixture of large or heavy hydrocarbon molecules which contain a significant amount of sulfur, nitrogen and oxygen. The extraction of bitumen from sand using hot water processes yields large volumes of fine tailings composed of fine silts, clays, residual bitumen and water. Mineral fractions with a particle diameter less than 44 microns are referred to as “fines.” These fines are typically clay mineral suspensions, predominantly kaolinite and illite.
The fine tailings suspension is typically 85% water and 15% fine particles by mass. Dewatering of fine tailings occurs very slowly. When first discharged in ponds, the very low density material is referred to as thin fine tailings. After a few years when the fine tailings have reached a solids content of about 30-35%, they are referred to as fluid fine tailings which behave as a fluid-like colloidal material. The fact that fluid fine tailings behave as a fluid and have very slow consolidation rates significantly limits options to reclaim tailings ponds. A challenge facing the industry remains the removal of water from the fluid fine tailings to strengthen the deposits so that they can be reclaimed and no longer require containment.
Accordingly, there is a need for an improved method to treat fine tailings to reduce their water content and reclaim the land on which fine tailings are disposed.